mptcp: options: suboptions sizes can be negative

Use a signed int for the returned size, because when other options are
dropped, the size can be negative, e.g. to send an echo ADD_ADDR with a
v4 address, and no port.

The behaviour is not changed, because it was working as expected with an
overflow. But it is clearer like this, and it will help later on.

Even if, for the moment, only the ADD_ADDR size can be negative in some
cases, a signed int is now used for all mptcp_established_options_*()
helpers, not to mismatch the type, and as a question of uniformity.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260605-net-next-mptcp-add-addr6-port-ts-v2-1-758e7ca73f4d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 70b939f3c33d88defe92ebdd043b351a07a9c3bd..fd972047fdf7c7c7db1744a3ccdc3f278c0000bb 100644 (file)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -447,8 +447,7 @@ static void clear_3rdack_retransmission(struct sock *sk)
 }
 
 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
-                                        bool snd_data_fin_enable,
-                                        unsigned int *size,
+                                        bool snd_data_fin_enable, int *size,
                                         struct mptcp_out_options *opts)
 {
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
@@ -560,8 +559,7 @@ static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 }
 
 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
-                                         bool snd_data_fin_enable,
-                                         unsigned int *size,
+                                         bool snd_data_fin_enable, int *size,
                                          struct mptcp_out_options *opts)
 {
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
@@ -658,8 +656,8 @@ static u64 add_addr_generate_hmac(u64 key1, u64 key2,
        return get_unaligned_be64(&hmac[SHA256_DIGEST_SIZE - sizeof(u64)]);
 }
 
-static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *skb,
-                                              unsigned int *size,
+static bool mptcp_established_options_add_addr(struct sock *sk,
+                                              struct sk_buff *skb, int *size,
                                               unsigned int remaining,
                                               struct mptcp_out_options *opts)
 {
@@ -706,8 +704,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
        return true;
 }
 
-static bool mptcp_established_options_rm_addr(struct sock *sk,
-                                             unsigned int *size,
+static bool mptcp_established_options_rm_addr(struct sock *sk, int *size,
                                              unsigned int remaining,
                                              struct mptcp_out_options *opts)
 {
@@ -736,8 +733,7 @@ static bool mptcp_established_options_rm_addr(struct sock *sk,
        return true;
 }
 
-static bool mptcp_established_options_mp_prio(struct sock *sk,
-                                             unsigned int *size,
+static bool mptcp_established_options_mp_prio(struct sock *sk, int *size,
                                              unsigned int remaining,
                                              struct mptcp_out_options *opts)
 {
@@ -763,7 +759,7 @@ static bool mptcp_established_options_mp_prio(struct sock *sk,
 }
 
 static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_buff *skb,
-                                                  unsigned int *size,
+                                                  int *size,
                                                   unsigned int remaining,
                                                   struct mptcp_out_options *opts)
 {
@@ -781,8 +777,7 @@ static noinline bool mptcp_established_options_rst(struct sock *sk, struct sk_bu
        return true;
 }
 
-static bool mptcp_established_options_fastclose(struct sock *sk,
-                                               unsigned int *size,
+static bool mptcp_established_options_fastclose(struct sock *sk, int *size,
                                                unsigned int remaining,
                                                struct mptcp_out_options *opts)
 {
@@ -804,8 +799,7 @@ static bool mptcp_established_options_fastclose(struct sock *sk,
        return true;
 }
 
-static bool mptcp_established_options_mp_fail(struct sock *sk,
-                                             unsigned int *size,
+static bool mptcp_established_options_mp_fail(struct sock *sk, int *size,
                                              unsigned int remaining,
                                              struct mptcp_out_options *opts)
 {
@@ -833,10 +827,10 @@ int mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 {
        struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
        struct mptcp_sock *msk = mptcp_sk(subflow->conn);
-       unsigned int opt_size = 0;
        int total_size = 0;
        bool snd_data_fin;
        bool ret = false;
+       int opt_size = 0;
 
        opts->suboptions = 0;
 
@@ -864,7 +858,7 @@ int mptcp_established_options(struct sock *sk, struct sk_buff *skb,
        if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, opts))
                ret = true;
        else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, opts)) {
-               unsigned int mp_fail_size;
+               int mp_fail_size;
 
                ret = true;
                if (mptcp_established_options_mp_fail(sk, &mp_fail_size,